JP-7-103105A (U.S. Pat. No. 5,355,859) shows a fuel supply system having a pressure sensor provided to a fuel rail and a control circuit controlling electricity supplied to a fuel pump based on an output of the pressure sensor. A plurality of fuel injectors are provided to the fuel rail. In this fuel supply system, a pulse width supplied to the injector has linearity to a fuel injection quantity injected by the injector.
The pressure in the fuel rail has various pressure components. However, the pressure sensor only detects pressure which is linear to the fuel injection quantity.
Further, the fuel pressure supplied from the fuel supply system includes pulsation components which indicate an operation condition of the fuel supply system. For example, the fuel pressure includes high frequency component which indicates an operation condition of an electric pump.
However, in the above fuel supply system, such a pulsation components are not detected by the pressure sensor. In other word, the pressure sensor is not utilized fully enough.
Further, the pressure sensor is provided to the fuel rail. Thus, a pulsation component due to the fuel pump may be attenuated at a position where the pressure sensor is positioned. Furthermore, a pulsation component due to the fuel pump is overlapped with a pulsation component due to the injector. Thus, it is relatively difficult to detect the pulsation component due to the pump.
Besides, in the above conventional system, there is no apparatus which detects a rotation speed of the pump. Thus, no control can be executed based on the rotation speed of the pump.